Liquid crystal mixture and light modulating device

ABSTRACT

Disclosed herein is a liquid crystal mixture applied in light compounds selected from the group of compounds of formula (I), component B comprised of one or more compounds selected from the group of compounds of formula (II), and component C comprised of one or more the liquid crystal mixture, wherein the liquid crystal mixture has higher stability of electrical performance and the light modulating device has improved optical performance.

TECHNICAL FIELD

The present invention relates to liquid crystals and devices using thesame, and more particularly, to a liquid crystal mixture and a lightmodulating device comprising the liquid crystal mixture.

BACKGROUND OF THE INVENTION

As a device exploiting the electro-optic effect, a liquid-crystal-basedlight modulating device is mainly comprised of transparent conductivesubstrates and liquid crystal materials, where the orientation of liquidcrystal molecules may be manipulated by applying an external electricfield to switch between different optical states. Because of theirunique characteristics, liquid-crystal-based light modulating devicesare used in a wide range of applications, such as building materials,home decoration devices, automotive displays, and consuming electronicdevices etc., for the realization of privacy, beautification andenergy-saving functions. Among them, a bistable or multi-stable lightmodulating device is highly desirable due to its energy-saving andfail-safe features.

A bistable light modulating device based on cholesteric liquid crystalsgenerally has two zero-electric-field-stable states: a transparent stateand a light scattering state. Due to its angular-independent hightransparency in the transparent state and high haze in the lightscattering state, the bistable cholesteric liquid crystal lightmodulating device has therefore very high market potential as a lightmodulation device in consumer electronics and as a building material.Generally, in this kind device, cholesteric liquid crystals form aperiodic spiral texture which is highly affected by the surfacecondition and external environment of the device. During application,the liquid crystal materials may become unstable due to the externalenvironment conditions, such as long-time-exposure to light, temperaturechanging, exposure to moisture and others, which cause the distributionof electron clouds of the liquid crystal molecules become abnormal. As aresult, the electro-optic performance of the light modulating device ischanged and the entire uniformity of the optical performance isdecreased, which not only affects the product appearance but also causesloss of the privacy, and ultimately limiting the further application ofthe light modulating device.

Therefore, there remains a need for a liquid crystal mixture whosestability can be increased while the light modulating device comprisethe liquid crystal mixture can maintain a high haze in the lightscattering state and a low haze in the transparent state, therebyimproving the stability of the electro-optic performance of the device.

SUMMARY OF THE INVENTION

In order to overcome the above issues, one objective of the presentinvention is to provide a liquid crystal mixture applied in lightmodulating devices, comprising:

component A comprised of one or more compound selected from the group ofcompounds of formula I

R₁-MG₁-X-MG₂-R₂  I;

component B comprised of one or more compounds selected from the groupof compounds of formula II

and component C comprised of one or more chiral compounds,

wherein R₁, R₂, R₃ and R₄ each independently denote —H, —F, —Cl or achain alkyl group with 1 to 25 C atoms where one or more H atom may beindependently substituted by halogen and one or more nonadjacent—CH₂—may be independently replaced by —O—, —CH═CH—, —CH═CF— or —CF═CF—,

MG₁ and MG₂ each independently denote a mesogenic group,

X is a straight-chain or branched alkyl group with 3-40 C atoms whereone or more —CH₂— may be independently replaced by —O—, —CH(F)—,—CH(Cl)— or —CH═CH— in such a manner that no two —O— or double bonds areadjacent to one another,

H₁, H₂ and H₃ each independently denote a ring structure selected fromthe group of

and their mirror structures where one or more H atoms may beindependently substituted by halogen or a alkyl group with 1-10 C atoms,

A₁ and A₂ each independently denote —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—,—CH═CH—, —CF₂CF₂—, —CF═CF—, —CH═CF—, a single bond or —(CH₂)_(a)— wherea is an even number between 2-10,

m is 0,1 or 2, n is 1, 2 or 3, o is 1 or 2, and m+n+o is no more than 5.

In order to modify the entire performance of the liquid crystal mixture,such as optical anisotropy, operating temperature range, solubility,elastic coefficient, viscosity coefficient and etc., the content of thecomponent B in the liquid crystal mixture should not be too low. In apreferred embodiment, the component B is more than 40% by weight of theliquid crystal mixture. In a more preferred embodiment, the component Bis 40%-95% by weight of the liquid crystal mixture.

The chiral compounds can induce the spiral twisting of nematic liquidcrystal molecules, forming chiral nematic liquid crystal (cholestericliquid crystal). In a preferred embodiment, the chiral compound isselected from the group of:

In some preferred embodiments, the mesogenic group is selected from thegroup of formula III

wherein,

H₄, H₅, H₆ and H₇ each independently denote a ring structure selectedfrom the group of

and their mirror structures, wherein one or more H atoms of the ringstructures may be independently substituted by halogen or a chain alkylgroup with 1-7 C atoms where one or more nonadjacent —CH₂— may bereplaced by —O— and one or more H atom may be substituted by F or Cl,

A₃, A₄ and A₅ each independently denote —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—,—CH₂CH₂—, —CF₂CF₂—, —CH═CH—, —CF═CF—, —CH═CF— or a single bond,

p and q each independently denote 0 or 1.

In some preferred embodiments, the mesogenic group each independentlycomprises at least two six-membered rings.

In some preferred embodiments, the mesogenic group is each independentlyselected from the group of

and their minor structures, wherein 1-4 H atoms of the six-membered ringmay be independently substituted by F, Cl or a chain alkyl group with1-7 C atoms where one or more nonadjacent —CH₂— may be replaced by —O—and one or more H atom may be substituted by F. In a more preferredembodiment, 1-4 H atoms of the six-membered ring may be independentlysubstituted by F, Cl, CH₃ or OCH₃.

In a preferred embodiment, X is a straight-chain or branched alkyl groupwith 5-25 C atoms where one or more —CH₂— may be independently replacedby —O—, —CH(F)—, —CH(Cl)— or —CH═CH— in such a manner that no two —O— ordouble bonds are adjacent to one another. In a more preferredembodiment, X is a straight-chain or branched alkyl group with 5-15 Catoms where one or more —CH₂— may be independently replaced by —O—,—CH(F)—, —CH(Cl)— or —CH═CH— in such a manner that no two —O— or doublebonds are adjacent to one another.

In some preferred embodiments, X is selected of formula IV

where Y₁ and Y₂ each independently denote —O— or a single bond, and s isan odd number between 3 and 13.

In some preferred embodiments, R₁ and R₂ each independently denote —H,—F, —Cl, —OCF₃, —OCHF₂, —CF₃ or an unsubstituted chain alkyl or alkoxylgroup with 1 to 10 C atoms. In a more preferred embodiment, R₁ and R₂each independently denote —F, —Cl, —OCF₃ or an unsubstituted chain alkylor alkoxyl group with 1 to 5 C atoms.

In some preferred embodiments, the compound of formula I is selectedfrom the group of compounds I-1 to I-21:

In some embodiments, the compound of formula I is further selected fromthe group of compounds I-2 to I-7.

In some preferred embodiments, the compound of formula II is selectedfrom the group of compounds II-1 to II-24:

In some embodiments, the compound of formula II is further selected fromthe group of compounds II-1 to II-16.

Another objective of the present invention is to provide a lightmodulating device containing the liquid crystal mixture, which includestwo stable states: the transparent state where substantially allincident light goes through and the light scattering state wheresubstantially all incident light is scattered.

In some preferred embodiments, the component A is 1%-60% by weight ofthe liquid crystal mixture. In a more preferred embodiment, thecomponent A is 10%-50% by weight of the liquid crystal mixture.

The invention provides a liquid crystal mixture that may be used inbistable light modulating device by introducing the compounds selectedfrom formula I and II and chiral compounds. The liquid crystal mixturehas higher stability of electrical performance, improving the stabilityof electro-optic performance of the device while the device maintains ahigh haze in the light scattering state and a low haze in thetransparent state, and thus improving the stability of opticalperformance of the device.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed description ofan illustrative embodiment of the present disclosure when read inconjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic, illustrative view of the structure of the lightmodulating device according to one embodiment;

FIG. 2 is a schematic, illustrative view of the structure of the lightmodulating device according to another embodiment;

FIG. 3 is a schematic, illustrative view of the structure of the lightmodulating device according to another embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The following description of the disclosed embodiments is provided indetail to enable any person skilled in the art to fully understand thepresent invention. However, it will be apparent to those skilled in theart to readily make or use the present invention without these specificdetails. In other examples, well-known structures and devices are shownin the block diagram. In this regard, the description of the differentillustrative exemplary embodiments presented herein are for the purposeof illustration and description and are not intended to be exhaustive orlimited to the inventive concept. Accordingly, the scope of theinvention is not to be limited by the specific embodiments describedabove, and is subject only to the scope of the appended claims.

The present invention discovers a liquid crystal mixture which can beapplied in light modulating devices. The liquid crystal mixturecomprises: component A comprised of one or more compound selected fromthe group of compounds of formula I: R₁-MG₁-X-MG₂-R₂; component Bcomprised of one or more compounds selected from the group of compoundsof formula II:

and component C comprised of one or more chiral compounds, wherein R₁,R₂, R₃ and R₄ each independently denote —H, —F, —Cl or a chain alkylgroup with 1 to 25 C atoms where one or more H atom may be independentlysubstituted by halogen and one or more nonadjacent —CH₂— may beindependently replaced by —O—, —CH═CH—, —CH═CF— or —CF═CF—; MG₁ and MG₂each independently denote a mesogenic group; X is a straight-chain orbranched alkyl group with 3-40 C atoms where one or more —CH₂— may beindependently replaced by —O—, —CH(F)—, —CH(Cl)— or —CH═CH— in such amanner that no two —O— or double bonds are adjacent to one another; H₁,H₂ and H₃ each independently denote a ring structure selected from thegroup of

and their minor structures where one or more H atoms may beindependently substituted by halogen or a alkyl group with 1-10 C atoms;A₁ and A₂ each independently denote —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—,—CH═CH—, —CF₂CF₂—, —CF═CF—, —CH═CF—, a single bond or —(CH₂)_(a)— wherea is an even number between 2-10; m is 0,1 or 2, n is 1, 2 or 3, o is 1or 2, and m+n+o is no more than 5.

The mesogenic group is selected from the group of formula III:

wherein H₄, H₅, H₆ and H₇ each independently denote a ring structureselected from the group of

and their minor structures, wherein one or more H atoms of the ringstructures may be independently substituted by halogen or a chain alkylgroup with 1-7 C atoms where one or more nonadjacent —CH₂— may bereplaced by —O— and one or more H atom may be substituted by F or Cl;A₃, A₄ and A₅ each independently denote —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—,—CH₂CH₂—, —CF₂CF₂—, —CH═CH—, —CF═CF—, —CH═CF— or a single bond; p and qeach independently denote 0 or 1.

Preferably, the mesogenic group each independently comprises at leasttwo six-membered rings. More preferably, the mesogenic group is eachindependently selected from the group of

and their minor structures, wherein 1-4 H atoms of the six-membered ringmay be independently substituted by F, Cl or a chain alkyl group with1-7 C atoms where one or more nonadjacent —CH₂— may be replaced by —O—and one or more H atom may be substituted by F. More preferably, 1-4 Hatoms of the six-membered ring may be independently substituted by F,Cl, CH₃ or OCH₃.

Preferably, X is a straight-chain or branched alkyl group with 5-25 Catoms where one or more —CH₂— may be independently replaced by —O—,—CH(F)—, —CH(Cl)— or —CH═CH— in such a manner that no two —O— or doublebonds are adjacent to one another. More preferably, X is astraight-chain or branched alkyl group with 5-15 C atoms where one ormore —CH₂— may be independently replaced by —O—, —CH(F)—, —CH(Cl)— or—CH═CH—in such a manner that no two —O— or double bonds are adjacent toone another. More preferably, X is selected of formula IV:

where Y₁ and Y₂ each independently denote —O— or a single bond, and s isan odd number between 3 and 13.

Preferably, R₁ and R₂ each independently denote —H, —F, —Cl, —OCF₃,—OCHF₂, —CF₃ or an unsubstituted chain alkyl or alkoxyl group with 1 to10 C atoms. More preferably, R₁ and R₂ each independently denote —F,—Cl, —O—CF₃ or an unsubstituted chain alkyl or alkoxyl group with 1 to 5C atoms.

Preferably, the compound of formula I is selected from the group ofcompounds I-1 to I-21:

Preferably, the compound of formula II is selected from the group ofcompounds II-1 to II-24:

The chiral compounds can induce the spiral twisting of nematic liquidcrystal molecules, forming chiral nematic liquid crystal (cholestericliquid crystal). Preferably, the chiral compound is selected from thegroup of:

Generally, the liquid crystal mixture was prepared in accordance withthe ratio specified in the following examples. The preparation iscarried out in accordance with a conventional method in the art. Indetail, each component is weighed according to its corresponding masspercentage, and placed in a glass bottle. After a magnetic stiffing baris added, the bottle is placed on a heating magnetic stirrer, and theliquid crystal mixture is heated and stirred until completely melting toform an isotropic transparent solution. The temperature at this pointhas reached the clear point of the liquid crystal mixture. If the liquidcrystal mixture contains a light-sensitive compound, the liquid crystalmixture must be heated to the clear point in the dark. The liquidcrystal mixture continues to be heat in the temperature for 30 minutesto ensure uniform mixing, and then the liquid crystal continues to bestirred for another 2 hours. In order to ensure sufficient and stablemiscibility of the liquid crystal mixture, as well as, forming of liquidcrystal state in an appropriate temperature range, the mass percentageof component B in the liquid crystal mixture should be more than 40%.Preferably, the mass percentage of the component B in the liquid crystalmixture is 40%-95%. The mass percentage of component A in the liquidcrystal is 1%-60%. Preferably, the mass percentage of component A is10%-50% in the liquid crystal mixture.

After that, the uniformly mixed liquid crystal mixture is poured into anempty liquid crystal cell prepared according to various designrequirements by a vacuum-filled method, and then the cell is sealed by aUV adhesive, forming a light modulating device. The light modulatingdevice has two stable states: a transparent state and a light scatteringstate. In the transparent state, the chiral nematic liquid crystal(cholesteric liquid crystal) molecules are substantially alignedparallel to the device substrate, and the helical axis thereof isperpendicular to the device substrate to form the planar texture ofcholesteric liquid crystal. In this state, the incident light transmitsthrough the light modulating device substantially unaffected. While inthe light scattering state, the cholesteric liquid crystal moleculesform a focal conic texture, and the incident light is substantiallyscattered, causing large haze. By selecting a suitable driving voltage,the light modulating device may be switched between the transparentstate and the light scattering state, where the haze is measured using aWGT-S type haze meter to determine its optical performance.

The structure of the light modulating device is shown in FIG. 1, whereinthe first transparent substrate 101 and the second transparent substrate102 may be made of a hard material (such as transparent glass) or aflexible material (such as PET, PEN, PC, PP, PMMA, PBT, PVC, PI,cellulose, etc.). The invention is not limited to this, and othermaterials with light transmission conforming to the requirements mayalso be used. The liquid crystal layer 103 is disposed between the firsttransparent substrate 101 and the second transparent substrate 102,which contains the liquid crystal mixture. The first transparentelectrode 104 is disposed between the first transparent substrate 101and the liquid crystal layer 103, while the second transparent electrode105 is disposed between the second transparent substrate 102 and theliquid crystal layer 103. Depending on its materials, the transparentelectrodes may be classified into carbon-based conductive films,metallic nanowire conductive films, and metallic oxide conductive films.In the following examples, the materials of the first transparentelectrode 104 and the second transparent electrode 105 is ITO. Thethickness of the liquid crystal layer 103 is 5-60 micrometers.

In some embodiments, a first alignment layer 106 may be disposed betweenthe first transparent electrode 104 and the liquid crystal layer 103, asshown in FIG. 2. The alignment layer 106 serves to align the liquidcrystal molecules in the liquid crystal layer 103 in a predeterminedpattern. In some embodiments, as shown in FIG. 3, a second alignmentlayer 107 may be further disposed between the second transparentelectrode 105 and the liquid crystal layer 103. Depending on the pretiltangle (i.e. the angle between the long axis of the liquid crystalmolecules and the surface of the alignment layer when the liquid crystalmolecules are sequentially arranged on the surface of the alignmentlayer), the alignment layer can be classified into homogenous alignmentwhere the long axis is substantially parallel to the surface, such asIPS, TN or STN type, or heterogeneous alignment where the long axis issubstantially vertical to the surface, such as VA type.

Under the external environment (such as long-term UV exposure, extremetemperature changes, exposure to moisture or dust, etc.), the liquidcrystal materials are easy to decompose and release ions. Excessive ioncharges will reduce the voltage holding rate (VHR) and resistivity ofthe liquid crystal materials, therefore affecting the electro-opticperformance. Meanwhile, excessive ion charges are accumulated on thecontact surface between the liquid crystal layer and the alignmentlayer, causing the effective voltage applied on the liquid crystalmolecules decreases with the accumulation of ion charges. As a result,the liquid crystal molecules cannot be rapidly rotated in the moment ofvoltage switching, affecting the stability and uniformity of opticalperformance of the light modulating device. In the following examples,the stability of electrical performance of the liquid crystal mixture isrevealed by measuring the drop in resistivity of the liquid crystalmixture. The resistivity is measured in the initial state, after UVirradiation (wavelength: 365 nm, light intensity: 85 mW/cm², exposuretime: 1 hour) and after heat treatment (temperature: 150° C., time: 1hour). The instrument used in the measurements is INSTEC ALCR-HR1resistance meter.

In the following examples, the component of the liquid crystal mixture,the optical performance of the light modulating device and the stabilityof electrical performance of the liquid crystal mixture will bedescribed in detail. The first transparent substrate 101 and the secondtransparent substrate 102 in the following examples are transparentglasses, and the first transparent electrode 104 and the secondtransparent electrode 105 are ITO. There are two alignment layer whichare both VA type.

In the following examples, the group structures of the liquid crystalmolecules are represented by the codes listed in Table 1, and the codesand structures of component C are listed in Table 2. The ratios allrefer to mass percentages.

TABLE 1 the code for groups of liquid crystal Code Group structure H

O —O— P

P¹¹

P¹²

P²¹

R²²

Q —CF2O— F —F N —CN E

n —C_(n)H_(2n+1) or —C_(n)H_(2n)—

where, if n=3, the group is —C₃H₇ (at the end of formula) or —C₃H₆— (inthe middle of formula).

TABLE 2 The code and structure of other additives Code Structure L-4

R05

COMPARATIVE EXAMPLE

TABLE 3 formula of liquid crystal mixture Component Ratio/% 5PPN 20.03PP¹¹PN 16.0 2PPN 7.0 5HPPN 9.0 5PPPN 4.0 5OPPN 16.0 6OPPN 8.0 4PEP¹¹N15.0 L04 5.0 Total 100

TABLE 4 optical performance data for the light modulating device andelectrical performance data for the liquid crystal mixture Electricalperformance Optical performance Resistivity (10¹² Ω-cm) Cell gap/μm 20Initial state 0.260 Initial state 0.150 Haze in the 48.0 After UV 0.004After heating 0.006 transparent state/% irradiation treatment Haze inthe light 79.7 Drop 98.46% Drop 96.00% scattering state/%

Example 1

TABLE 5 formula of liquid crystal mixture Component Ratio/% Component AFP¹²P9PP¹¹F 15.0 Component B 3PP¹¹P2 4.0 3HPP²¹F 4.0 5HPP²¹F 8.0 3HPP11F4.0 5HPP¹¹F 4.0 3PP¹¹P²¹F 8.0 3HHPP²¹F 8.0 3HHP¹¹P²¹F 8.0 3PP²¹QP²¹F 8.03PP¹¹P²¹QP²¹F 8.0 4PP¹¹P²¹QP²¹F 8.0 5PP¹¹P²¹QP²¹F 8.0 Component C L045.0 Total 100

TABLE 6 optical performance data for the light modulating device andelectrical performance data for the liquid crystal mixture Electricalperformance Optical performance Resistivity (10¹² Ω-cm) Cell gap/μm 20Initial state 11.33 Initial state 10.97 Haze in the 7.6 After UV 4.69After heating 5.31 transparent state/% irradiation treatment Haze in thelight 78.2 Drop 58.61% Drop 51.60% scattering state/%

Example 2

TABLE 7 formula of liquid crystal mixture Component Ratio/% Component AFP¹²P7PP¹¹F 29.9 Component B 3HPO1 1.2 3PP¹¹P2 3.1 3HPP²¹F 4.3 5HPP²¹F7.9 2PP¹¹P²¹F 2.4 3PP¹¹P²¹F 6.1 3HHPP²¹F 4.9 3HHP¹¹P²¹F 1.83PP¹¹P²¹QP²¹F 9.8 4PP¹¹P²¹QP²¹F 9.8 5PP¹¹P²¹QP^(2I)F 9.8 Component C L049.0 Total 100

TABLE 8 optical performance data for the light modulating device andelectrical performance data for the liquid crystal mixture Electricalperformance Optical performance Resistivity (10¹² Ω-cm) Cell gap/μm 20Initial state 11.80 Initial state 11.44 Haze in the 0.8 After UV 6.20After heating 6.27 transparent state/% irradiation treatment Haze in thelight 75.3 Drop 47.46% Drop 45.19% scattering state/%

Example 3

TABLE 9 formula of liquid crystal mixture Component Ratio/% Component AFP¹²P7PP¹¹F 29.0 FPP¹²O7OP¹¹PF 1.0 Component B 3PP¹¹P2 3.3 3HPP²¹F 3.35HPP²¹F 6.5 3HP¹¹P²¹F 3.3 3HPP¹¹F 3.3 3PP¹¹P²¹F 5.2 3HHPP²¹F 6.54HHPP²¹F 6.5 3PP²¹QP²¹F 6.5 3PP¹¹P²¹QP²¹F 7.6 4PP¹¹P²¹QP²¹F 6.55PP¹¹P²¹QP²¹F 6.5 Component C L04 5.0 Total 100

TABLE 10 optical performance data for the light modulating device andelectrical performance data for the liquid crystal mixture Electricalperformance Optical performance Resistivity (10¹² Ω-cm) Cell gap/μm 20Initial state 13.70 Initial state 12.99 Haze in the 1.2 After UV 6.59After heating 6.86 transparent state/% irradiation treatment Haze in thelight 79.9 Drop 51.90% Drop 47.19% scattering state/%

Example 4

formula of liquid crystal mixture Component Ratio/% Component AFP¹²P7PP¹¹F 10.0 FP¹²P9PP¹¹F 10.0 FP¹²P¹¹PP¹¹F 10.0 Component B 3PP¹¹P23.3 3HPP²¹F 3.3 5HPP²¹F 6.5 3HPP¹¹F 3.2 5HPP¹¹F 3.2 3PP¹¹P²¹F 6.53HHPP²¹F 6.5 3HHP¹¹P²¹F 6.5 3PP²¹QP²¹F 6.5 3PP¹¹P²¹QP²¹F 6.54PP¹¹P²¹QP²¹F 6.5 5PP¹¹P²¹QP²¹F 6.5 Component C L04 5.0 Total 100

TABLE 12 optical performance data for the light modulating device andelectrical performance data for the liquid crystal mixture Electricalperformance Optical performance Resistivity (10¹² Ω-cm) Cell gap/μm 50Initial state 12.50 Initial state 13.08 Haze in the 5.7 After UV 5.93After heating 6.89 transparent state/% irradiation treatment Haze in thelight 91.2 Drop 52.56% Drop 47.32% scattering state/%

Example 5

TABLE 13 formula of liquid crystal mixture Component Ratio/% Component AFP¹²P7PP¹¹F 28.0 3HP7PH3 1.0 FPPP7PPPF 1.0 Component B 3PP¹¹P2 3.33HPP²¹F 3.3 5HPP²¹F 6.5 3HPP¹¹F 3.2 5HPP¹¹F 3.2 3PP¹¹P²¹F 6.5 3HHPP²¹F6.5 3HHP¹¹P²¹F 6.5 3PP²¹QP²¹F 6.5 3PP¹¹P²¹QP²¹F 6.5 4PP¹¹P²¹QP²¹F 6.55PP¹¹P²¹QP²¹F 6.5 Component C L04 5.0 Total 100

TABLE 14 optical performance data for the light modulating device andelectrical performance data for the liquid crystal mixture Electricalperformance Optical performance Resistivity (10¹² Ω-cm) Cell gap/μm 20Initial state 13.40 Initial state 12.57 Haze in the 6.1 After UV 6.54After heating 6.32 transparent state/% irradiation treatment Haze in thelight 78.8 Drop 51.19% Drop 49.72% scattering state/%

Example 6

TABLE 15 formula of liquid crystal mixture Component Ratio/% Component AFP¹²P7PP¹¹F 30.0 FP¹²P9PP¹¹F 5.0 Component B 3PP¹¹P2 3.0 3HPP²¹F 3.05HPP²¹F 6.5 3HPP¹¹F 3.0 5HPP¹¹F 3.0 3PP¹¹P²¹F 6.5 3HHPP²¹F 6.53HHP¹¹P²¹F 6.5 3PP²¹QP²¹F 6.5 3PP¹¹P²¹QP²¹F 6.5 4PP¹¹P²¹QP²¹F 6.55PP¹¹P²¹QP²¹F 6.5 Component C R05 1.0 Total 100

TABLE 4 optical performance data for the light modulating device andelectrical performance data for the liquid crystal mixture Electricalperformance Optical performance Resistivity (10¹² Ω-cm) Cell gap/μm 20Initial state 12.90 Initial state 11.94 Haze in the 1.1 After UV 6.01After heating 6.23 transparent state/% irradiation treatment Haze in thelight 75.8 Drop 53.41% Drop 47.82% scattering state/%

Example 7

TABLE 17 formula of liquid crystal mixture Component Ratio/% Component AFP¹²P7PP¹¹F 30.0 FP¹²P11PP¹¹F 10.0 Component B 3PP₁₁P2 2.8 3HPP²¹F 2.85HPP²¹F 5.5 3HPP¹¹F 2.7 5HPP¹¹F 2.7 3PP¹¹P²¹F 5.5 3HHPP²¹F 5.53HHP¹¹P²¹F 5.5 3PP²¹QP²¹F 5.5 3PP¹¹P²¹QP²¹F 5.5 4PP¹¹P²¹QP²¹F 5.55PP¹¹P²¹QP²¹F 5.5 Component C L04 5.0 Total 100

TABLE 18 optical performance data for the light modulating device andelectrical performance data for the liquid crystal mixture Electricalperformance Optical performance Resistivity (10¹² Ω-cm) Cell gap/μm 20Initial state 11.70 Initial state 11.32 Haze in the 1.0 After UV 6.05After heating 6.07 transparent state/% irradiation treatment Haze in thelight 68.8 Drop 48.29% Drop 46.38% scattering state/%

From the above examples and comparative example, it is demonstrated thatthe light modulating device containing the liquid crystal mixture of thepresent invention has a significantly low haze in the transparent stateand an ultra-high haze in the light scattering state, thereby providinghigh light transmittance while keeping sufficient privacy and isolation.Meanwhile, After UV irradiation or heating treatment, the drop degree ofresistivity in examples 1-7 is significantly smaller than that in thecomparative example, indicating stability of electrical performance ofthe liquid crystal mixture in examples 1-7 is improved.

While several particular exemplary embodiments have been described abovein detail, the disclosed embodiments are considered illustrative ratherthan limiting. Those skilled in the art will readily realize thatalternatives, modifications, variations, improvements, and substantialequivalents are possible without substantially departing from thenovelty spirits or scope of the present disclosure. Thus, all suchalternatives, modifications, variations, improvements, and substantialequivalents are intended to be embraced within the scope of the presentdisclosure as defined by the appended claims.

INDUSTRIAL APPLICABILITY

The liquid crystal mixture of the present invention can be applied tothe field of liquid crystal.

1. A liquid crystal mixture applied in light modulating devices,comprising: component A comprised of one or more compounds selected fromthe group of compounds of formula IR₁-MG₁-X-MG₂-R₂  I; component B comprised of one or more compoundsselected from the group of compounds of formula II

and component C comprised of one or more chiral compounds, wherein R₁,R₂, R₃ and R₄ each independently denote —H, —F, —Cl or a chain alkylgroup with 1 to 25 C atoms where one or more H atom may be independentlysubstituted by halogen and one or more nonadjacent —CH₂— may beindependently replaced by —O—, —CH═CH—, —CH═CF— or —CF═CF—, MG₁ and MG₂each independently denote a mesogenic group, X is a straight-chain orbranched alkyl group with 3-40 C atoms where one or more —CH₂— may beindependently replaced by —O—, —CH(F)—, —CH(Cl)— or —CH═CH— in such amanner that no two —O— or double bonds are adjacent to one another, H₁,H₂ and H₃ each independently denote a ring structure selected from thegroup of

and their mirror structures where one or more H atoms may beindependently substituted by halogen or a alkyl group with 1-10 C atoms,A₁ and A2 each independently denote —CF₂O—, —OCF₂—, —CH₂O—, —OCH2—,—CH═CH—, —CF₂CF₂—, —CF═CF—, —CH═CF—, a single bond or —(CH₂)_(a)— wherea is an even number between 2-10, m is 0,1 or 2, n is 1, 2 or 3, o is 1or 2, and m+n+o is no more than
 5. 2. The liquid crystal mixture asdefined in claim 1, wherein the component B is more than 40% by weightof the liquid crystal mixture.
 3. The liquid crystal mixture as definedin claim 1, wherein the mesogenic group is each independently selectedfrom the group of formula III

wherein, H₄, H₅, H₆ and H₇ each independently denote a ring structureselected from the group of

and their mirror structures, wherein one or more H atoms of the ringstructures may be independently substituted by halogen or a chain alkylgroup with 1-7 C atoms where one or more nonadjacent —CH₂— may bereplaced by —O— and one or more H atom may be substituted by F or Cl,A₃, A₄ and As each independently denote —CF₂O—, —OCF₂, —CH₂O—, —OCH₂—,—CH₂CH₂—, —CF₂CF₂—, —CH═CH—, —CF═CF—, —CH═CF— or a single bond, p and qeach independently denote 0 or
 1. 4. The liquid crystal mixture asdefined in claim 3, wherein the mesogenic group each independentlycomprises at least two six-membered rings.
 5. The liquid crystal mixtureas defined in claim 4, wherein the mesogenic group is each independentlyselected from the group of

and their mirror structures, wherein 1-4 H atoms of the six-memberedring may be independently substituted by F, Cl or a chain alkyl groupwith 1-7 C atoms where one or more nonadjacent —CH₂— may be replaced by—O— and one or more H atom may be substituted by F.
 6. The liquidcrystal mixture as defined in claim 1, wherein X is selected of formulaIV

where Y₁ and Y₂ each independently denote —O— or a single bond, and s isan odd number between 3 and
 13. 7. The liquid crystal mixture as definedin claim 1, wherein R₁ and R₂ each independently denote —H, —F, —Cl,—OCF₃, —OCHF₂, —CF₃ or an unsubstituted chain alkyl or alkoxyl groupwith 1 to 10 C atoms.
 8. The liquid crystal mixture as defined in claim1, wherein the chiral compound is selected from the group of


9. A light modulating device comprising the liquid crystal mixture asdefined in claim 1, including two stable states: a transparent statewhere substantially all incident light goes through and a lightscattering state where substantially all incident light is scattered.10. The light modulating device as defined in claim 9, wherein thecomponent A is 1%-60% by weight of the liquid crystal mixture.